Tom Leonard was born in Dublin, and worked much of his life in a family business in the Dublin Corporation Wholesale Fruit and Vegetable Markets. The business had been started two generations earlier by his grandmother, continued by his father and ultimately passed to Leonard and his two brothers. While in business, Leonard was also a Dublin City Councillor.

Leonard did not contest the 1987 general election as Fianna Fáil dispensed with his candidacy from the party ticket in favour of John Stafford and Dermot Fitzpatrick. Despite the fact that it was highly unusual for a sitting TD not to be permitted to defend his seat and faced with considerable negative press on the matter, Leonard graciously accepted the party decision which ended his Dáil career and went back to being a city councillor.[3]

He continued in the markets until his retirement, and died in Blanchardstown, Dublin in 2004.